Ephemerides for celestial bodies

Overview of ephemerides models

There are several ephemerides models available in CelestLab to compute the position and velocity of bodies of the solar system:

• Meeus model for the Sun

  This is a very simple analytical model.

  The origin is the Earth and the frame is the ecliptic of date (EOD).

  Reference: Astronomical Algorithms J.Meeus - Second edition 1998, Chapter 25

• Meeus model for the Moon

  This is an analytical model of medium complexity.

  The maximum number of harmonics to compute the longitude, latitude and distance is 62, 66 and 46.

  The origin is the Earth and the frame is the ecliptic of date (EOD).

  Reference: Astronomical Algorithms J.Meeus - Second edition 1998, Chapter 47

• VSOP87 model for solar system bodies

  This is an analytical model of high complexity.

  The full model uses thousands of harmonics for each variable (longitude, latitude, distance).

  The origin is the Sun and the frame is the ecliptic of date (EOD).

  Reference: Planetary Theories in rectangular and spherical variables: VSOP87 solution. Bretagnon P., Francou G.

• ELP/MPP02 model for the Moon

  This is an analytical model of high complexity.

  The full model uses dozens of thousands of harmonics for each variable (longitude, latitude, distance).

  The origin is the Earth and the frame is the ecliptic of date (EOD).

  Reference: LUNAR SOLUTION ELP version ELP/MPP02 - Jean CHAPRONT and Gerard FRANCOU Observatoire de Paris - SYRTE department - UMR 8630/CNRS - October 2002

• JPL's DE405 ephemerides for solar system bodies

  The ephemerides are obtained by interpolation in pre-computed data stored in binary files, and thus are available only for a limited period of time ([1960-2200] by default, the maximum time span being [1600-2200]). The binary files are Scilab binary files made from the original ascii files that can be downloaded from: ftp://ssd.jpl.nasa.gov/pub/eph/planets/ascii/de405.

  Reference: NASA/JPL ephemerides

General information about the models complexity and accuracy is given in the following table :

See CelestLab functions : CL_eph_moon, CL_eph_sun, CL_eph_planet and CL_eph_de405.

Planet barycenters

All the models are compared to DE405 although DE405 gives the position of the barycenter of the planet and its satellites (except for Earth). In practice it doesnt matter because the accuracy of the models are below the angular separation of the planet and the barycenter of the planet: